In recent years, the semiconductor industry has experienced rapid growth due to continuous improvement in integration density of various electronic components, e.g. transistors, diodes, resistors, capacitors, etc. For the most part, this improvement in integration density has come from successive reductions in minimum feature size, which allows more components to be integrated into a given area. Currently, integrated fan-out packages are becoming increasingly popular for their compactness. In the integrated fan-out packages, planarization of the molding compound and formation of the redistribution circuit structure plays an important role during packaging process.